EPOW - Ecology Picture of the Week

Each week a different image of our fascinating environment is featured, along with a brief explanation written by a professional ecologist.

23 February - 1 March 2009

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Glacial Shrinkage in the Andes

Volcan Lanin, Andes Mountains
Argentina, South America

Credit & Copyright: Dr. Bruce G. Marcot

Explanation:  Towering some 12,388 feet (3,776 meters) into the clouds is this massive extinct volcano that straddles Argentina and Chile in the southern Andes Mountains of South America at nearly 40 degrees south latitude below the equator.  

Volcan Lanin itself is actually a composite of four major geological periods of eruption and a number of layers, and is termed a compound stratocone.  

But although the eruptions have subsided -- with the last eruption in the Holocene -- the ice is alive with daily meltwater.  The glaciers are melting.


Just a few decades ago, 
a glacier filled the trough 
in the lower part of this 
photo of the slopes of 
Volcan Lanin.  

Studies have shown significant "retreat" of glaciers in the Andes Mountains in recent decades, apparently because of the warming of the atmosphere and lessening precipitation.  Research on a nearby volcano, Volcán Mocho-Choshuenco, showed a 40% reduction in the area of glacier cover between 1976 and 2003.  

Snow, ice, and glaciers on Volcan Lanin are melting.

When glaciers melt, there is often a positive feedback effect leading to even faster melting.  The melting first uncovers darker-colored rock which then absorbs sunlight and heat far more effectively than did the reflective white of the ice and snow, so the land warms even more quickly.  In these photos of Volcan Lanin, compare the dark exposed slopes to the white of the glacial ice.  

Melting of glaciers can have serious effects on humans.  Mountain glaciers provide an ecosystem service of providing fresh water to people in many parts of the world, especially the tropics.  Loss of glaciers in the Andes could threaten the loss of water to 30 million people.  In one report, the Chacaltaya Glacier in Bolivia has nearly disappeared completely.   

Melting of alpine glaciers can have many ripple effects.
In the southern Andes Mountains, changes in climate,
water runoff, cloud formation, precipitation, and temperature
could drastically alter local vegetation and habitats for plants and animals.
Shown here is a stand of "monkey puzzle trees" in which I found a
flock of Austral Parakeets feeding on the seed cones.  How 
changes in this vegetation might affect the trees, birds, and other wildlife
is unknown.

     Rivera, A., F. Bown, G. Casassa, C. Acuña, and J. Clavero. 2005. Glacier shrinkage and negative mass balance in the Chilean Lake District (40°S). Hydrological Sciences Journal 50(6):963-974.


Next week's picture:  The Dancing Deer of Asia

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